49.2 Prof. Odling on the Natural Groupings 



Group XII. — Mercury, Lead, Silver. 



I believe myself warranted in associating these three metals 

 into one family. Their points of resemblance are as decided as 

 those presented in other groups, though the circumstance of 

 the differences not being always gradational, throws some little 

 doubt upon the subject. The sequence of the atomic weights is 

 very marked : — 



Hg = 100 311-6 _ ,^o.o 



Pb = 103-6 -3 ^"'^^• 



Ag = 108 



Sum 311-6 Mean difference = 4. 



The atomic volumes, as determined by Kopp, exhibit a similar 

 though not so exact a sequence. 



Hg = 93 337 _,,„.„ 



Pb = 114 -3- - ^'''^'^' 



Ag = 130 

 Sum 337 



Their specific gravities are associated in a corresponding- 

 manner. 



Hg = 13-6 35-35 _ ^ ^- 



Pb = 11-35 ~3 ^^■'^• 



Ag = 10-4 



Sum 35-35 



The specific heat of silver is double that of mercury and lead. 

 The three metals are readily fusible, — mercury at — 40° C, lead 

 at 320° C, silver at 1000° C. All three metals are capable of 

 volatilization, — mercury most readily, then lead, then silver. All 

 three metals crystallize in octahedra, are soft and malleable. 

 Solid mercury, like lead, is capable of being cut with a knife. 

 All three metals form protoxides and protosalts. The oxide of 

 mercury has a brick-red or orange-yellow colour, the oxide of lead 

 is pale yellow or dull red, the oxide of silver is brown. All three 

 become much darker by heating. The oxygen in each oxide has 

 the same atomic volume, although Kopp assigns a volume to the 

 oxygen of oxide of silver, different from the oxygen-volume of 

 the other two oxides. Thus with mercui-y — 



Calculated. Experimental. 

 135*^ Sp. gr. Sp. gr. 



Qg gg = 10-8 11-OBoullay, ll-2Karsteu; 



with lead, — 



l^4,ni) = 9'5 9*5 Boullay, 9*2 Karsten ; 



